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1
Rainwater Management
for
Increased Agricultural production
Centre of African Studies – Porto- Portugal 2 – 3 October 2008
CONFERENCE ON WATER IN AFRICA
SESSION ON WATER AND AGRICULTURE
Nico van Leeuwen
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Outline
• Food for all ?
• Key role of water
• Smallholder adapted technologies
• Where does the rainwater go ?
• Options for management of rainwater
• Conclusions
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< 2.52.5–45–19
20–34≥35
No data
% undernourished
UNDERNOURISHMENT
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UNDERNOURISHMENT IN THE WORLD
• 776 million people in developing countriesremain undernourished
• World Food Summit goal (1996) to reduce undernourishment to 410 million but present expectations are 610 million
• Seven out of ten of the world's poor live in rural areas and depend on agriculture
• Arid zones cover 45% of the world area
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< 2.52.5–45–19
20–34≥35
No data
% undernourished
UNDERNOURISHMENT SUB- SAHARA AFRICA
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UNDERNOURISHMENT IN SUB-SAHARAN
AFRICA
• SSA undernourishment rose from 200 m people in 1995 to 450 m today.
• SSA population 62% in rural areas
• SSA rural poverty accounts for 90% of total poverty
• SSA 80% of the poor depend on agriculture
• 38 % of SSA is arid land
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< 2.52.5–45–19
20–34≥35
No data
% undernourished
Undernourishment and water scarcity Sub- Sahara Africa
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Dry land areas and rain fed agriculture
Definition and distribution of dry land areas
Classifica-tion
Length of growing period for annual
crops in days*
% of World
Land area
% of land area Sub-Saharan
Africa Hyper arid 0 19 24 arid 1 – 59 7 6 semi-arid 60 – 119 20 13 dry-sub humid
120 - 179 18 19
Arid land: 45% of world area, 38% of Sub-Saharan Africa
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Strong relationship between water availability and cereal production
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In order to reach the World Food Summit and Millennium goals
• to reduce the number of undernourished
• and feed the world population expected toincrease by 30% over the next 30 years
world food production should
be increased by 50 % in 2030
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Some realities:
•The green revolution is slowing down
•Serious environmental problems are appearing
•Investment in agriculture and irrigation has been reduced
•Groundwater resources are dangerously low in many countries
Yield increase 66 %
Arable land
expansion 22 %Cropping
intensity 12 %
How to grow 50 % more food in 2030
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Yield Increase: •Adequate water supply to crops through Irrigation, water harvesting/runoff farming.•Improved seed•Fertiliser•Agricultural practices
Arable land expansion•Irrigate dry areas•Expand use of wetlands•Water harvesting on arid lands
Cropping intensity •Expand and improve irrigation•Reclamation and intensive use of wetlands
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Large irrigation projects for small number of farmers ?orSmall-scale water development for a large numberof farmers?
In developing countries
• 80% of the farmers are smallholder farmers
• practicing mainly subsistence farming
• located largely in arid and semi-arid zones or zones with erratic rainfall
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Improvement of water supply to crops
• accessible and affordable • to poor,• smallholder• subsistence farmers
Most appropriate technologies for smallholder farmers:
• Very-small-scale irrigation (with groundwater, surface water or collected/stored rainwater
• Water management in wetlands and valley bottoms
• Management of water from rainfall.
16(Rockström, Fox, Persson et Falkenmark(SIWI)
RAINWATER MOVEMENTS
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Rainwater distribution in arid areas
(Rockström, Fox, Persson et Falkenmark(SIWI)
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Improved use of rainwater
• Prevent run-off
• Reduce evaporation from soil surface
• Keep water in the root zone en prevent deep percolation
Options:
• Conservation agriculture
• Rainwater harvesting – run-off farming
“Rainwater that falls on my land remains on my land”
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CONSERVATION AGRICULTURE
• No tillage
• Maintain coverage on soil surface
• Stimulate biological functioning of the soil
• Reduces evaporation and run-off
Conservation agriculture only works when rainfall is sufficient
20Small-scale conservation agriculture
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Permanent soil coverage
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Mechanized conservation agriculture
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Run-on area= storage in the soil profile or in a reservoir
Runoff area
= catchment
The collection of runoff for its productive use
• Water applied to the crop and stored in the soil
profile: runoff farming
• Water stored in a reservoir for future use : irrigation,
Domestic use, livestock, aquaculture, etc
Rainwater Harvesting
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Potential areas for runoff farming
Zone P/ETP Annualrainfall
Suitability Length GrowingPeriod
Hyperarid
< 0.05 < 100 mm Too dry for runoff farming
0 day
Arid 0.05 – 0.2 100 < x <200 mm
Suitable for runoff farming
1 – 59days
Semi-arid
0.21 – 0.5 200 < x < 400 mm
Suitable for runoff farming
60 – 119days
Dry sub-humid
0.5 – 0.65 400 < x < 800 mm
Suitable for runoff storage
120 – 179days
Humid > 0.65 > 800 mm Too wet for runoff farming
> 179 days
Source: GAEZ (FAO – IIASA, 2003)
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Microcatchment Macrocatchment
Floodwater harvesting
Types of run-off farming water harvesting
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Small-scale rainwater harvesting (zai)
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Tree planting for reforestation or land rehabilitation
28Inter-row water harvesting in orchard in arid area
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ADVANTAGE :
• coverage of 10-15 ha / day
width 0.40 m
length 4 -5 m
depth 0.40 m
DIMENSIONS :
DISADVANTAGE :
• high investment costs
Microcatchments made by the “Dolphin-plough”
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31Mechanized runoff farming
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Rainwater harvesting or conservation •Very small scale •Large scale
Keita project in Niger FAO/Italy and WFP 1984 – 199913 000 km² - 300,000 people living in 400 villages
• 50 artificial lakes• 42 dams• 65 village wells• 10,000 ha water conservation• 16 million trees• Infrastructure: schools, maternity centres, veterinary facilities, storehouses, micro-credit, literacy courses, etc.
33
Keita project Niger
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Keita project Niger
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1
3
1
3
2
Example:
Keita (Niger) 2
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Characteristics of run-off farming techniques
• Oriented towards increased agricultural production
• Reduces risks of crop failure and encourages other investments (seed, fertilizer, etc)
• Relatively Low-Cost and high return of investment
• Immediate benefits to farmers
• Reduces downstream flooding and consequent damages
more……
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• Contributes to increased recharge of groundwater
• Protects and rehabilitate the environment
• Combat desertification
• Alleviates the negative impact of climate change on water resources
Characteristics of run-off farming techniques
38
Rainwater management:
a new green revolution ?
Thanks for your attention
Merci pour votre attention
Obrigado